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Home , Adrenal medulla, Corpora arenacea, Herring bodies, Parathyroid gland, Pars intermedia, Pars tuberalis

Introduction The slides for this lab are located in the “” folders on the Virtual Microscope. In this lab, you will learn about the structures of the major endocrine organs

Endocrine organs are ductless that secrete signaling molecules called into the blood stream. Signaling molecules have a physiological effects on other cells throughout the body. Hormones can regulate growth and and their effects are usually widespread. We will be focusing on six endocrine organs in this lab:

o Pituitary o Parathyroid glands o o Pineal body o gland o Pancreas Each of these glands has several cells that have different functions. In order to develop a good understanding of these endocrine organs you need to locate these cell, identify their signaling molecule secretions and determine their physiological function.

Learning objectives and activities Using the Virtual Slidebox:

A Identify the and distinguish between the adenohypophysis and neurohypophysis based on the cellular components of these regions.

B Locate the three zones of the and find chromaffin cells in the .

C Identify a thyroid follicle, its components and surrounding parafollicular cells.

D Classify oxyphil and chief cells within the .

E Locate and sand in the .

F Review the structure of the pancreas and identify the islets of Langerhans.

G Complete the self-quiz to test your understanding and master your learning. Identify the pituitary gland and distinguish between the adenohypophysis and neurohypophysis based on the cellular components of these regions

Examine Slide 1 and Slide 2 to identify the adenohypophysis, neurohypophysis & their regions.

An understanding of the organization of the pituitary and its is essential before interpreting the histological sections.

supra optic paraventricular nucleus nucleus

optic chiasma infundibulum (neural stalk) hypothalamo-hypophyseal tract

pars nervosa

pars distalis Rathke’s cysts

anterior lobe posterior lobe (adenohypophysis) (neurohypophysis) Examine Slide 1 and Slide 2 to identify the cells and features of the adenohypophysis.

i. Adenohypophyis Identify a. Capsule the gland capsule in A dense irregular connective tissue capsule surrounds the gland. Slide 1a and Slide 2a b. Pars tuberalis Identify The tubular portion of the adenohypophysis that surrounds the pars tuberalis in neural stalk (infundibulum) to form the . It contains Slide 1b and Slide 2b mainly basophilic gonadotrophic cells that secrete LH and FSH. It contains the long hypophyseal portal vessels.

c. Pars intermermedia Identify The region of the adenophypophysis that abuts the pars nervosa pars intermedia in of the neurohypophysis. It contains Rathke’s cysts. Slide 1c and Slide 2c

d. Rathke’s cysts Identify Fluid filled cysts within the pars intermedia. They are remnants of Rathke’s cysts in Rathke’s pouch, a space that develops in the oral as it Slide 1d and Slide 2d folds and moves upwards to form the gland during development.

e. Pars distalis The largest part of the adenohypophysis that is located most Locate the distal to the brain. It contains acidophils and basophils of all types pars distalis in and chromophobe cells. Slide 1e and Slide 2e

f. Basophils These cells are basophilic cells that are either: - thyrotrophs that secrete Thyroid Stimulating (TSH) Identify - adrenocorticotrophs that secrete Adrenocorticotrophic Hormone basophils in (ACTH) Slide 1f and Slide 2f - gonadotrophs that secrete (LH) and Follicle Stimulating Hormone (FSH)

g. Acidophils Identify These cells are eosinophilic cells that are either: acidophils in - mammotrophs that secrete (PRL) Slide 1g and Slide 2g - somatoptrophs that secrete (GH)

h. Chromophobes Identify These cells are pale, unstained stem cells that differentiate to chromophobes in replace acidophils and basophils in the adenohypophysis. Slide 1h and Slide 2h Examine Slide 1 and Slide 2 to identify the cells and features of the neurohypophysis.

ii. Neurohypophysis

i. Infundibulum Identify Surrounded by the pars tuberalis of the adenohyophyis. Note that the infundibulum and the infundibulum contains the of the neurons that have hypothalamo- their cell bodies located within the supraoptic and paraventircular hypophseal tract in nuclei of the . This tract is known as the Slide 1i and Slide 2i hypathalmo-hypophyseal tract (see diagram below).

j. Pars nervosa The most distal part of the neurophypophysis found next to the Identify pars intermedia of the adenohypoophysis. It contains the vascular pars nervosa in plexus of the pars nervosa into which the hormones Antidiuretic Slide 1j and Slide 2j Hormone (ADH) and are released.

k. Identify The glial cells that support the axons located within the pituicytes in neurohypophysis. They do not secrete hormones. Slide 1k and Slide 2k

l. Identify Swellings of axons packed full of neurosecretory granules, they can Herring bodies in be a variety of colors depending on the stain used. Slide 1l and Slide 2l

Supraoptic nucleus Paraventricular nucleus

infundibulum hypothalamo-hypophyseal tract ADH

pars nervosa

Oxytocin Locate the three zones of the adrenal cortex and find chromaffin cells in the adrenal medulla.

The adrenal glands are a pair of glands that lie near the superior pole of the kidneys. The gland’s stroma is a rich network of reticular fibers supporting secretory cells which has two distinct and concentric layers: - adrenal cortex: derived from mesoderm and contains secreting cells - adrenal medulla: derived from and contains modified sympathetic postganglionic neuron that specialized for secretion.

Use Slide 3 to identify the following key features of the adrenal cortex i. Adrenal cortex a. Capsule Locate the adrenal A dense irregular connective tissue capsule which extends into capsule in the gland forming trabecular septa Slide 3a b. Identify the zona Secretory cells are organized into ‘glomeruli’ that produce the glomerulosa mineralocorticoid . Slide 3b c. Identify the zona Secretory cells are organized into long cords with parallel fasciculata capillaries that produce the glucocorticoid . Slide 3c

d. Identify the zona Secretory cells are organized into short irregular cords that reticularis produce the weak that is Slide 3d converted to in other tissues.

ii. Medulla

e. Chromaffin cells Examine the Modified post-synaptic sympathetic neurons that contain chromaffin cells in the granules of epinephrine and that are released adrenal medulla in during the fight or flight response. The cells vary in the intensity Slide 3e of their staining because norepinephrine granules stain more ‘red’ than epinephrine granules. Identify a thyroid follicle, its components and surrounding parafollicular cells.

The thyroid gland has a connective tissue capsule. It is composed of spherical units called follicles.

Use Slide 4 to locate the key features of the thyroid gland.

a. Capsule Identify the thyroid The gland is surrounded by a dense irregular connective tissue capsule capsule. Slide 4a b. Follicles Thyroid follicles are lined by follicular cells composed of a simple cuboidal epithelium. The follicles contain colloid, a substance composed of thyroglobulin and iodide (iodinated thyroglobulin) Identify follicles, that is produced by follicular cells. Under the influence of TSH follicular cells and from the adenohyopophysis the follicular cells also pinocytose colloid in colloid and convert it to T3/T4 before releasing it into Slide 4b parafollicular blood vessels.

c. Parafollicular cells (C-cells) Identify the Clusters of pale staining cells that secrete the hormone parafollicular cells . Slide 4c

High blood

Parafollicular cells  calcitonin

Anterior pituitary

Basophil (thyrotrophic)

TSH Follicular cells  iodinated thyroglobulin (colloid) converted Thyroxin (T4) aka thyroid Triiiodothyronine (T3) hormone Classify oxyphil and chief cells within the parathyroid gland.

The parathyroid gland appears as a small oval mass at the posterior aspect of the thyroid (there are four in the body, only one is seen this slide). As a result, they are often seen in the same section as the thyroid gland. The gland changes with age becoming fattier and developing more inactive cells (oxyphils). i. Parathyroid (young)

Use Slide 5 to identify the following features of the parathyroid gland of a young individual.

a. Capsule Examine the capsule A dense irregular connective tissue capsule surrounds the gland of the parathyroid in and is continuous with that of the thyroid gland. Slide 5a

b. Chief cells Examine the Cells with large nuclei lined up to form cords that appear to snake organization of chief through the gland. The cells secrete (PTH). cells in the parathyroid Endothelial lined blood vessels filled with red cells appear as in Slide 5b islands between cords. ii. Parathyroid (old)

Use Slide 6 to identify the following features of the parathyroid gland of an older individual.

a. Capsule Identify the capsule in Identify the capsule in this slide. Slide 6a

b. Chief cells Identify chief cells in The cells exhibit a less distinct cord-like organization in this slide. Slide 6b c. Oxyphil cells Sparse, large cells that are eosinophilic. They also secrete PTH but Identify oxyphil cells in to a lesser extent – deemed inactive cells in aged parathyroids. Slide 6c

d. Identify adipocytes in The number of adipocytes deposited within the older parathyroid Slide 6d gland is significant. Low blood calcium

Chief cells  parathyroid hormone (PTH)

Oxyphil cells  parathyroid hormone (PTH)

Locate pinealocytes and brain sand in the pineal gland.

On microscopic section, without special stains, it is difficult to discern the structure of this gland. It is a projection of the third ventricle and as such is often seen containing cerebrospinal fluid (CSF)

Use Slide 7 to identify the following features of the pineal gland.

a. Capsule Examine the capsule in The gland is enclosed by a fine capsule composed of pia mater Slide 7a which extend into the gland to form lobules.

b. Lobules Locate examples of Lobules are surrounded by pia mater and contain pinealocytes lobules in Slide 7b and supportive glial cells.

c. Pinealocytes Find pinealocytes in Arranged in clumps and are more basophilic than surrounding Slide 7c supportive cells. Pinealocytes secrete

d. Corpora aranacea This is brain sand. Clumps of calcium and magnesium phosphate Find brain sand in that are found in the pineal glands of older individuals. Their Slide 7d function is not known. Darkness

Pinealocytes  melatonin

Review the structure of the pancreas and identify the islets of Langerhans.

Review the organization of the exocrine components of the pancreas then look for the endocrine component scattered around the .

Use Slide 8 to identify islets of Langerhans in the pancreas

a. Islets of Langerhans The major cells in the islets are alpha cells that secrete Glucagon Examine the capsule in and beta cells that secrete . You cannot tell the difference Slide 8a between the different cell types with traditional stains.

Low blood sugar

alpha islet cells  glucagon

beta islet cells  insulin

High blood sugar In addition to all the basic tissues in slides you must be able to identify the following structures and their features:

Pituitary Adenohypophysis Pars distalis Parathyroid Pars intermedia Chief cells Pars tuberalis Oxyphil cells Acidophils Adipocytes Basophils Chromophobes Adrenal Rathke’s cyst Adrenal cortex Long (hypophyseal) portal Zona Primary venous plexus glomerulosa Secondary venous plexus Zona fasciculata Zona reticularis Neurohypophysis Sinusoids Pars nervosa Capsule Infundibulum Hypothalamo-hypophyseal tract Adrenal medulla Pituicytes Chromaffin cells Herring bodies Pineal Thyroid Pinealocytes Follicles Follicular cells Lobules Colloid Brain sand, Parafollicular cells, c-cell, clear cells Pancreas All features from Digestive lab Islets of Langerhans